Multi-head switching arrangement for non-percussive printer

ABSTRACT

A multi-head switching arrangement in a non-percussive type printer which generates each character as a pattern of dots. The switching arrangement eliminates interference between heads by causing them to operate in a particular spatial sequence. The arrangement is such as to reduce to a minimum the number of highspeed switching elements used, while ensuring the elimination of the residual field problems which causes interference between closely arranged adjacent heads.

United States Patent [151 3,681,775 Mason et al. [451 Aug. 1, 1972 [54] MULTI-HEAD SWITCHING (56] References Cited ARRANGEMENT FOR NON- PERCUSSlv-E PRINTER v UNITED STATES PATENTS 2,844,811 7/1958 Burkhart ..340/174.l D [72] Inventors: Frederick Percival Mason, Burgess 3 9 44 4 l 1 Brian Michael Patience, East ,32 ,9 7/1967 Lemberger et al.....3 0/ 74. D boume both of England Primary Examiner-Bernard Konick [73] Assignee: Creed & Company Limited, Sussex, Bummer-Gary Hoffma AttorneyC. Cornell Remsen, Jr. et al. England [22] Filed: June 24, 1971 [57] ABSTRACT [2]] Appl. No.2 1 ,217 A multi-head switching arrangement in a non-percussive type printer which generates each character as a pattern of dots. The switching arrangement eliminates [52] U.S. Cl ..346/74 M, 340/ 174.1 D, 346/74 ES interference between heads by causing them to [51] Int. Cl. ..Gllb 5/44 operate in a particular spatial Sequence The arrange [58] Field of Search ..340/ 174.1 D, 174.1 G;

346/74 ES, 74 E, 74 S, 74 SB, 74 SC, 74 CH,

ment is such as to reduce to a minimum the number of high-speed switching elements used, while ensuring the elimination of the residual field problems which causes interference between closely arranged adjacent heads.

3 Claim, 3 Drawing Figures Iw Q E Q.

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PATENTEDAUB' 1 m2 SHEET 2 OF 3 Inventors FRDRICK P. MASON BRIAN M. PAT/ENCE gent PATENTED M18 1 I97? 3. 6 81, 7 75 sum 3 [1F 3 meow/cw P. MASON BRIAN M. AT/Eyes Agent MULTI-IIEAD SWITCHING ARRANGEMENT FOR. N ON-PERCUSSIVE PRINTER BACKGROUND OF THE INVENTION linear array of recording heads is utilized to generate the printed characters as dot patterns and in which the heads can be used singly or in pairs to record a dot in producing these patterns, the apparatus, as it is used at ever higher speeds of printing, can be expected to have some deterioration of print quality because of time lag effects in the recording heads. Thus in a ferrographic printer for example if, in two adjacent heads one has just finished printing as the other begins, the decaying magnetic field of the first may interfere adversely with the growing field of the second. Comparable effects may be experienced in a thermographic printer.

SUMMARY OF THE INVENTION According to the present invention there is provided a head switching arrangement for a non-percussive printing apparatus which includes a linear array of nonpercussive current-operated recording heads, a character generator for generating a character as a pattern of dots in a rectangular array of dot positions, and a sequence generator for generating a sequence of control signals, in which a switching matrix under the control of the signals from the sequence generator diverts current from one head to another of said linear array in such a sequence that no pair of consecutively operated heads is adjacent, so that time-lag effects cannot cause the first-operated head of the pair to interfere with the second-operated head of the pair.

According to the present invention there is also provided a head switching arrangement for a non-percussive printing apparatus which includes a linear array of non-percussive, current-operated recording heads, a character generator for generating a character as a pattern of dots in a rectangular array of dot positions, and a sequence generator for generating a sequence of control signals, in which each head has a first current terminal and a second current terminal, in which the linear array of heads is divided into a plurality of groups of not more than n heads per group, in which a first rank of two-terminal switch elements has n members, each of which has its first terminal connected to the first terminal of all similarly positioned heads in each group, in which the members of said first rank are divided into m equal sections, the members of each section being connected to adjacent heads in each group and having their second terminals commoned, in which a second rank of two terminal switch elements contains m members each of which has a first terminal connected to the commoned second terminals of a different one of said m sections, in which said second rank is divided into q equal sub-groups, the members of a subgroup not being connected to adjacent sections of the first rank, and having their second terminals commoned, in which a third rank of two-terminal switch elements contains q members each having its first terminal connected to the commoned second terminals of minal connected to a first terminal of a supply of cur-' rent for operating said heads, in which in each group of heads the second terminals are commoned, in which a fourth rank of two-terminal switching elements contains as many members as there are groups of heads, each member having its first terminal connected to one of the commoned second terminals of a different one of said groups, in which the second terminals of alternate members of said fourth rank are commoned, in which a fifth rank of two-terminal switch elements has two members, each having a first terminal connected to a different one of the commoned terminals of said fourth rank, and its second terminal connected to the second terminal of said supply of current, in which said character generator produces a succession of signals signifying the presence or absence of dots at different positions along said linear array, in which said sequence generator produces a sequence of control signals which control the ranks of switching elements so that only one head or pair of heads is operated at a time and so that two consecutively operated heads are not adjacent, said q members of said third rank operating one after the other and each being closed for not more than the time needed to record one dot, said m members of said second rank operating one after the other and each being closed for at least the time needed to record one dot, said members of said fourth rank operating one after the other and each being closed for at least the time needed to record n dots, and said members of the fifth rank operating in turn, and being closed for not more than the time needed to record n dots, and in which the speed of response of the switch elements of the third and fifth ranks is at least four times that of the other switch elements.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention is described below with reference to the accompanying drawings, in which:

FIG. 1 is a schematic drawing illustrating the head DESCRIPTION OF THE PREFERRED EMBODIMENT .In FIG. 1, which is a highly schematic drawing of a particular embodiment, there is shown at R1 to R part of a linear array of recording heads. Heads R1 to Rl0'are used in the recording of the first character in a line of characters, heads R11 to R20 in the recording of the second character, and so on. Characters are formed by recording dots at selected positions in the first row of each character, and then, as the recording medium is moved for example upwards relative to the line of heads, in the second row, and so on until all the characters in a line of characters are complete. A character is thus formed from a pattern of dots in selected positions of a rectangular array, for example a 10 X 15 array of possible dot positions. Whether a dot is recorded or not is determined by the state, open or closed, of a two terminal switch element associated with a recording head, for example D1 and R1 in FIG. 1. By a two terminal switch element is meant any device capable of controlling the current supply to the head and having two terminals which carry that current; it will, for high speeds of printing, almost certainly be a solid state device. The switch symbol used in the diagram is intended as a completely general symbol and is not to be taken to indicate merely an mechanical contact element. Forty switch elements, D1 to D40, are shown. Each is associated with more than one head; D1 is associated for example with heads R1, R41 and so on, D2 associated with heads R2 and R42 and so on; and in general a switch element Dx is associated with the heads Rx R(x 40) and so on. The switch elements D are controlled as explained hereinafter by a dot pattern generator.

Each of the four decades of switch elements D is commoned and connected to a further switch element G, the first decade D1 to D being so connected to switch element G1, and so on. In turn, switch elements G1 and G3 are commoned and connected to switch element H1, and switch elements G2 and G4 are commoned and connected to switch elements H2. These last two elements are connected to one terminal of a supply of current for energizing the recording heads.

At the side of the heads remote from the switch elements D the first 40 heads are commoned and connected to a switch element G5, the second 40 heads are commoned and connected to a switch element G6 and so on. In turn odd numbered switch elements G5, G7 and so on are commoned and connected to a switch element H3, while even-numbered switch elements G6, G8 and so on are commoned and connected to a switch element H4. These last two elements are connected to the other terminal of the supply of the current for the recording heads.

It is now obvious that any recording head in the array can be energized by closing appropriate ones of the various switch elements H, G, and D. Thus head R1 is energized when switch elements H1, G1, D1, G5, and H3 are all closed. If heads were energized sequentially, that is head R1, followed by head R2, followed by head R3, and so on, and if adjacent dots in a given row in any character were to be printed then the time lag effect mentioned above would cause deterioration of the print quality and, moreover, the D switch elements would need to operate at maximal dot speed, that is the highest speed at which dots are to be printed. To avoid the time lag effect and to reduce the number of switch elements which must be capable of maximal dot speed the switch arrangement is operated as now described.

In order to have a printing of a first character in a line of print, i.e. by heads Rl-R10, switch elements H1, G1, H3, G5 and, if a dot is to be printed by head Rl, switch element D1 are closed and remain so for a period of time sufficient to cause head R1 to print effectively, which period is referred hereinafter as T. At the end of period T switch elements H1, G1, and D1 are allowed to open; element H1 is a fast acting element, i.e. at least four times as fast as a G switch element, and immediately breaks the current through head R1, even though the slower acting elements G1 and D1 have not yet opened. While head R1 was being energized. switch elements G2 and D11 (if a dot is to be printed by head R11) were closed, preparing a path for current through head R11 in preparation for the recording of the first dot row of the second character in the line of print. When switch element H1 opens,

switch element H2 immediately closes and stays closed so that head R11 is energized for the period T. During this second period switch elements G3 and D21 (if head R21 is to print) have been closed, and switch element G1 has opened. At the end of period T switch element H2, while like H1 is fast acting, opens and H1 closes again so that current can be diverted to head R21. H1 remains closed for a further period T during which the switch elements G2 and D11 are opening and the switch elements G4 to D31 (if required) are closing. At the end of this third period T switch element H1 opens and H2 closes and current is diverted to head R31 if it is to print. At the end of this last period T four dots have, if required, been printed, in corresponding positions in each of four consecutive characters, the heads being well separated from each other so that time lag effects are negligible. The process is then repeated so that heads R2, R12, R22 and R32 can be energized and so on until head R40 is energized (if required).

At the end of the period of energization of head R40 not only does switch element H2 open but also H3, ad both H1 and H4 close. Switch element G6 can have been closed several periods T before this and element G5 can now take several periods T to open. Now switch elements H1, G1, D1 (if required), G6 and H2 are closed, and drive current is directed to head R41. The whole process is repeated until head R is energized (if needed), when switch element G6 is opened, G7 having closed several periods T previously, and switch elements H1 and H3 are closed and H2 and H4 opened. The process is then repeated for a further group of heads and so on until all the heads in the linear array have had an opportunity to be energized, and all the dots to be printed in the first row of a line of characters have been printed. The whole process is then repeated for the second row of dots in each character in the line of print, and so on until the complete line of characters has been printed.

It can be seen that although switch elements H1, H2, H3 and H4 must change state (open or close) in small fractions of the period T,-switch elements G1, G2, G3 and G4 can take almost the whole of a period T to change state, switch elements D1, D2, etc. can take almost four periods T to open or close, and switch elements G5, G6, etc. can take even longer than four periods T, although in the particular arrangement shown all the elements G1 to G4 and all the D elements open or close in the same time, that is a little less than the period T. This is because of the way the dot information is fed to the D switch elements.

In FIG. 2 is shown a dot pattern generator P which produces at each period T a signal to control the next switch element D to be connected to the supply of cur rent for energizing the heads. The dot generator P feeds this signal to one or the other of two storage elements, S1 and S2 depending on which of switch elements H1 and H2 is closed. The outlet of storage element S1 is connected to an inlet of each of AND-gates C1 to C10 and the outlet of storage element S2 is connected to an inlet of each of'AND-gates C11 to C20. The output of AND-gate C1 controls both switch elements D1 and D21, that of gate C2 controls D2 and D22 and so on.

A sequence generator W provides all the control signals which ensure that the apparatus works in the correct sequence. From this sequence generator are obtained the-control signals hl and k2 which not only control respectively the switch elements H1 and H2 but also the storage elements S2 and S1. Thus for example, at a time when switch element H1 is closed by signal I11, and head R1 is or is not energized, depending on the state of D1 which in turn depends on the state of storage element S1, the storage element S2 is being set to correspond to the output signal from dot generator P under control of signal hl, and when H2 is closed, S1 will be set under control of signal h2. The AND-gates Cl, etc., are also controlled by signals t1 to r20. Thus during the time that signal t1 is active the switch elements D1 and D21 will both be set to correspond to the state of storage element S1 but during the first part of 1 current is diverted to D1 by switch element G1 and during the last part of 11 current is diverted to D21 by G3. It can now be seen why elements D must work as fast as elements G1 to G4, for if element D1 is closed as well as D3 when G3 is closed then it must be fully opened again by the time Gl closes to divert current to element D2, otherwise there will be a false print from head R1 and elements G1 and H1 will probably be overloaded. Signal :2 overlaps signal d sc that during the middle part of signal t1 switch elements D11 and D31 are set to correspond to the state of storage element S2, and are set again after signal 11 has ended.

In a practical arrangement all the switches and the recording heads would be rated for pulsed operation and would be damaged if a fault were to happen which caused any combination of switches to remain permanently closed and deliver continuous current. To avoid such damage, the switches H1, H2, H3, and H4 are pulse generators coupled by transformers into the arrangement at the appropriate points, the common connection of H1 and H2 then being directly connected to that H3 and H4.

FIG. 3 shows the relative timing of some of the signals generated by the sequence generator W; those not shown can easily be interpolated by one versed in the art. The top line of each trace represents the signal present or on, the bottom line represents the signal absent or off and hatching shows that the state of the signal is dependent on whether or not a dot is to be printed. The dotted lines indicate the response of switch elements which the signal controls. It can be seen that signals h3 and k4 alternate at every 40 dot periods; signals g 1, g2, g3, and g4 repeat after every 4 dot periods and each is staggered by one dot period from its predecessor; signals g5, g6, g7 etc. occur once in every complete row of dots each signal being on for a little over 40 dot periods and the on period of each signal being about 40 dot periods later than its predecessor. The diverting of current from one group of 40 heads to an adjacent'group is done by the switch elements H3 and H4, the elements G5, G6, G7 etc., merely preparing the path in advance. The signal p from the pattern generator P changes for every successive dot period and the signals s1 and s2 change at half that rate. The signals t1 to r each last for 4 dot periods, with the even-numbered signals lagging by l dot period behind the preceding odd-numbered signal, and odd-numbered signals lagging by 3 dot periods behind the preceding even-numbered signal.

While the principles of this invention have been described above in connection with specific apparatus, it is to be understood that this description is made only by way of example and not as a limitation to the scope of the invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

l. A head switching arrangement for a non-percussive recording/printing apparatus of the type including a linear array of non-percussive current-operated recording heads, comprising a switching matrix coupled' to the array of recording heads, a character generator coupled to said switching matrix for causing a character to be generated by said recording heads as a pattern of dots in an array of dot positions, and a sequence generator coupled to said switching matrix for providing a sequence of control signals thereto, wherein said switching matrix is caused to divert current from one head to another of said linear array in a sequence in which no pair of consecutively operated heads is adjacent, whereby time-lag effects are prevented from causing the first-operated head of the pair to interfere with the second.

2. A head switching arrangement for a non-percussive printing apparatus of the type including a linear array of non-percussive, current-operated recording heads, comprising a character generator generating a character as a pattern of dots in a rectangular array of dot positions, and a sequence generator for generating a sequence of control signals, wherein each recording head has a first current terminal and a second current terminal, and the linear array of heads is divided into a plurality of groups having n heads per group, in which a first rank of two-terminal switch elements has n members, each of which has its first terminal in each group, in which the members of said first rank are divided into m equal sections, the members of each section being connected to adjacent heads in each group and having their second terminals commoned, in which a second rank of two terminal switch elements contains m members each of which has a first terminal connected to the commoned second terminals of a different one of said m sections, in which said second rank is divided into q equal subgroups, the members of a sub-group having their second terminals commoned, in which a third rank of two terminal switch elements contains q members each havingits first terminal connected to the commoned second terminals of a different one of said q sub-groups and its second terminal connected to a first terminal of a supply of current for operating said heads, in which in each group of heads the second terminals are commoned, in which a fourth rank of two-terminal switching elements contains as many members as there are groups of heads, each member having its first terminal connected to one of the commoned second terminals of a different one of said groups, in which the second terminals of alternate members of said fourth rank are commoned, in which a fifth rank of two-terminal switch elements has two members, each having a first terminal connected to a different one of the commoned terminals of said fourth rank, and its second terminal connected to the second terminal of said supply of current, in which said character generator produces a succession of signals signifying the presence or absence of dots at different positions along said linear array, in which said sequence generator produces a sequence of control signals which control the ranks of switching elements so that only one head is operated at a time and so that two consecutively operated heads are not adjacent, said q members of said third rank operating one after the other and each being closed for not more than the time needed to print one dot, said m members of said second rank operating one after the other and each being closed for at least the time needed to permit one dot, said members of said fourth rank operating one after the other and each being closed for at least the time needed to print n dots, and said members of the fifth rank operating in turn, and being closed for not more than the time needed to print n dots, and in which the speed of response of the switch elements of the third and fifth ranks is at least four times that of the other switch elements.

3. The switching arrangement as claimed in claim 2, in which the number of members in each of the m sections of said first rank is equal to the number of dot positions in the width of said rectangular array. 

1. A head switching arrangement for a non-percussive recording/printing apparatus of the type including a linear array of non-percussive current-operated recording heads, comprising a switching matrix coupled to the array of recording heads, a character generator coupled to said switching matrix for causing a character to be generated by said recording heads as a pattern of dots in an array of dot positions, and a sequence generator coupled to said switching matrix for providing a sequence of control signals thereto, wherein said switching matrix is caused to divert current from one head to another of said linear array in a sequence in which no pair of consecutively operated heads is adjacent, whereby time-lag effects are prevented from causing the first-operated head of the pair to interfere with the second.
 2. A head switching arrangement for a non-percussive printing apparatus of the type including a linear array of non-percussive, current-operated recording heads, comprising a character generatoR generating a character as a pattern of dots in a rectangular array of dot positions, and a sequence generator for generating a sequence of control signals, wherein each recording head has a first current terminal and a second current terminal, and the linear array of heads is divided into a plurality of groups having n heads per group, in which a first rank of two-terminal switch elements has n members, each of which has its first terminal in each group, in which the members of said first rank are divided into m equal sections, the members of each section being connected to adjacent heads in each group and having their second terminals commoned, in which a second rank of two terminal switch elements contains m members each of which has a first terminal connected to the commoned second terminals of a different one of said m sections, in which said second rank is divided into q equal sub-groups, the members of a sub-group having their second terminals commoned, in which a third rank of two terminal switch elements contains q members each having its first terminal connected to the commoned second terminals of a different one of said q sub-groups and its second terminal connected to a first terminal of a supply of current for operating said heads, in which in each group of heads the second terminals are commoned, in which a fourth rank of two-terminal switching elements contains as many members as there are groups of heads, each member having its first terminal connected to one of the commoned second terminals of a different one of said groups, in which the second terminals of alternate members of said fourth rank are commoned, in which a fifth rank of two-terminal switch elements has two members, each having a first terminal connected to a different one of the commoned terminals of said fourth rank, and its second terminal connected to the second terminal of said supply of current, in which said character generator produces a succession of signals signifying the presence or absence of dots at different positions along said linear array, in which said sequence generator produces a sequence of control signals which control the ranks of switching elements so that only one head is operated at a time and so that two consecutively operated heads are not adjacent, said q members of said third rank operating one after the other and each being closed for not more than the time needed to print one dot, said m members of said second rank operating one after the other and each being closed for at least the time needed to permit one dot, said members of said fourth rank operating one after the other and each being closed for at least the time needed to print n dots, and said members of the fifth rank operating in turn, and being closed for not more than the time needed to print n dots, and in which the speed of response of the switch elements of the third and fifth ranks is at least four times that of the other switch elements.
 3. The switching arrangement as claimed in claim 2, in which the number of members in each of the m sections of said first rank is equal to the number of dot positions in the width of said rectangular array. 